OF THE TONGUES OP THE MAMMALIA. 13 



the external vallate papillae of the lateral rows, and extending 

 forwards to a point level with the posterior extremity of the 

 mesial sulcus. The numbers of ridges and elevations are as 

 follows : — 



Right organ : Length 1*3 cm. Ridges 11. Sulci 12. 

 Left organ : Length 1"35 cm. Ridges 12. Sulci 13. 



In his study of the tongue of the foetal Gorilla, Deniker (17) 

 has shown that the lateral organs are better developed than in 

 the adult. 



The ridges and sulci just cut the lateral borders of the tongue. 

 They are long, narrow, and tapering ; some are twisted and some 

 have secondary fissures. 



The Inferior Surface (text-fig. 3 B). 



The inferior surface presents for examination a papillary 

 border, a frenum, a sublingual fold, two plica? fimbriata?, a mesial 

 crest, and a mesial sulcus which has already been described. It 

 has, therefore, the same structures as the tongue of the Chim- 

 panzee, Avith the mesial crest in addition. 



The papillary border maintains the same width across the 

 under surface of the apex, but it widens out from before 

 backwards along the lateral borders. It bears conical and 

 fungiform papilla? whose method of disposition is of the usual 

 type (text-fig. 3 B, a). 



The most notable feature is a row of closely-set club-shaped 

 conical papilla? bounding the zone internally (text-fig. 3 B, f). 

 They increase in size from before backwards, and they lie fiat 

 against the surface of the tongue. Some are entire and others 

 are subdivided into lobules as shown in text-fig. 3 D, d. In no 

 other Anthropoid tongue is there a uniform row of these papilla?. 



The mesial crest, or plica mediana, is a fold of mucous mem- 

 brane occupying the ventral mesial sulcus (text-fig. 3 B, d). It 

 runs along the anterior border of the frenum, and thins out and 

 disappears on the dorsal surface of the sublingual fold. Deniker 

 (17) considers that it is a remnant of the sublingua of the 

 Prosimia?. 



The plica} fimbriatae (text-fig. 3 B, b) are united anteriorly at 

 the posterior border of the papillary zone on the inferior surface. 

 When they are traced backwards they diverge and become wider 

 and more prominent. They have undulating free margins, and 

 are pale in colour. The mucosa between them is pale and the 

 remainder is pink in preserved specimens, so the plica? and inter- 

 vening part together look like a sublingua. A vertical section of 

 the tongue of the Gorilla resembles that of the Chimpanzee 

 (text-fig. 1 D). 



The frenal lamella., or sublingual fold, is triangular in shape 

 and has a rounded entire apex (text-fig. 3 B, g). Wharton's 

 Ducts open on its dorsal surface, and the bristles shown in 

 text-fig. 3 B, e, pass into them, 



